It is desirable to connect certain electronic components, such as but not limited to disc drive read/write heads and amplifiers for example, in a manner which minimizes the inductance of the interconnect. Lower inductance is desirable to increase the operational frequency of such electronic components. For example, in a conventional disc drive for a personal computer, the operational frequency of the read/write head is a function of the inductance of the circuit comprising the head, the conductors, the amplification device, and perhaps other interconnection components. Specifically, a read function of a disc drive can be modeled as a low-pass filter. The read frequency at which a signal is dramatically attenuated is inversely proportional to the total circuit inductance, of which the inductance of the insulated conductors is a major factor. Accordingly, a decrease in the inductance of the insulated conductors of the disc drive circuit results in a similar decrease in the total circuit inductance, and a nearly proportional increase in the allowable read frequency. This of course increases the quantity of data which can be read per unit of time. A similar effect may also occur with a write function of a disc drive.
A common type of interconnect for a disc drive is a parallel or twisted thin wire pair. The individual coated wires of this wire pair typically have a diameter of about 35 .mu.m, which corresponds to an AWG of 48. These wires may carry a balanced (or differential) signal pair, or may provide a signal path and a return path for a single-ended signal. The inductance of a conventional disc drive circuit may be significantly decreased by insulating the individual wires of the circuit with an extremely thin layer of insulation.
In addition to the apparent need for conductors having extremely thin insulation for the purpose of reducing inductance, many electronic devices, such as modem medical devices for example, require electrical conductors of extremely small dimensions. Such conductors may have a diameter of less than 25 .mu.m, which would correspond to an AWG of 52 or less. Often these conductors must be insulated with a material having a uniform thickness which is much less than the nominal cross-sectional dimension of such conductors.
Conventional insulation methods, such as extrusion and tape wrapping, work with reasonable success when the required insulation thickness is not much less than the cross-sectional dimensions of the conductor. However, these methods are not suited for insulating conductors having extremely small dimensions with a uniform layer of insulation having a thickness which is substantially less than the cross-sectional dimension of the conductor itself. For example, as the insulation thickness is reduced, any displacement between the axis of a conductor and the axis of the insulation results in unacceptable variations in the thickness of the insulation and/or exposed conductor surface. Accordingly, extrusion processes are not effective to achieve a uniform layer of insulation of substantially less than 0.001 inches. Additionally, in a tape wrapping insulation process, the insulation thickness of a single layer of tape is limited by the tensile strength of the tape. Excessive reductions in the thickness of the tape produces a tape which is too weak to be handled by readily available equipment and methods. Accordingly, tape wrapping processes are limited to insulation thicknesses of about 0.001 inches or larger. Conventional tape wrapping machines are also not designed to manipulate extremely thin conductors, such as AWG 52 sized wires, without damaging these extremely thin conductors. Dip-coating processes have also been used to apply insulation to conductors. This method is somewhat conformal, but the thickness which can be achieved is limited by the viscosity and surface tension of the solution and by other process parameters. Also, a dip-coating process is not particularly effective for insulating an extremely thin conductor with a substantially pinhole free layer of insulation having a thickness of less than about 30 .mu.m.
In addition to the foregoing, U.S. Pat. No. 3,616,389 discloses a process for insulating a conductor by electrophoretically precipitating an insulating coating from a water dispersion of a resin vamish onto the surface of a conductor. By use of this process, insulation coatings having a thickness of from 30 microns to 500 microns were claimed to have been achieved. Although these coatings may have operated with varying degrees of success, there is a need to provide an electrical conductor having an insulation thickness of substantially less than 30 microns to minimize the inductance of an electrical circuit. Additionally, there is a need to provide an electrical conductor having an insulation thickness which is substantially less than the cross-sectional dimension of the electrical conductor.
The foregoing illustrates limitations known to exist in present insulated conductors. Thus, it is apparent that it would be advantageous to provide an improved insulated electrical conductor directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.